This invention relates to an apparatus for making crisscross-wound layers to produce fiber-reinforced, rotationally symmetrical wound bodies. The apparatus includes a rotatable winding mandrel and a carriage which is displaceable back and forth parallel to the mandrel axis and which carries a thread laying system including stationary thread guiding rollers and thread laying rollers which are swingable about the axis of a common pivotal support. At least the thread laying rollers are provided with circumferential grooves for the guidance and simultaneous deposition, on the mandrel, of several, parallel-extending, resin-saturated fiber filaments or threads.
Wound bodies made of threads, such as glass fiber, Kevlar fiber or carbon fiber threads and an adhesive, such as synthetic resin are formed, as a rule, by circumferentially wound or crisscross-wound layers.
The circumferentially wound layers, wherein the threads are deposited substantially in a circumferential direction on the winding mandrel with a relatively small feed of the carriage supporting the laying roller, result in a high strength in the circumferential direction of the body.
The crisscross-wound layers, wherein the threads are deposited on the mandrel in steep helices with a relatively large feed of the carriage supporting the laying roller, result in a high strength of the wound body in the axial direction as well as in a high bending strength. The helical crisscross windings are usually deposited in laying angles of approximately .alpha.=45.degree. to 90.degree., as measured in the circumferential direction of the mandrel. Since helical windings have to be applied in both directions, positive and negative winding angles appear.
A thread laying system of the above-outlined type including a pivotal laying roller pair for an individual thread is disclosed in U.S. Pat. No. 4,359,356 issued Nov. 16, 1982. As shown in FIG. 5 of the patent, the thread is advanced approximately perpendicularly to the winding mandrel axis to a guide roller which is mounted on the outer circumference of a frame affixed to a carriage. The frame is provided with an aperture in which a hollow shaft oriented towards the winding mandrel is pivotally mounted. The thread laying roller pair is carried at the end of the hollow shaft. The thread running from the guide roller passes through the hollow shaft and is alternately deposited on the winding mandrel by one and the other laying roller.
In order to shorten the time for making the crisscross-wound layers, it is in principle possible to deposit simultaneously a plurality of fiber strands on the winding mandrel. Such an arrangement, however, involves the problem that between the individual fiber strands on the winding mandrel undesired gaps appear because of the intermediate webs between the grooves of the laying rollers.